Hitherto, chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) have been used as refrigerants for air-conditioning apparatuses (refrigeration and air-conditioning apparatuses). However, because chlorine included in the molecule of these refrigerants deplete the ozone layer in the stratosphere, CFC has already been abolished completely and regulation of production of HCFC has begun.
Alternatively, air-conditioning units that employ hydrofluorocarbon (HFC) that does not include any chlorine in its molecule are put into practical. When an air-conditioning unit using CFC or HCFC becomes deteriorated, since these refrigerants are abolished or regulation is imposed on production thereof, renewal to an air-conditioning unit using HFC is required.
Further, overhauling including renewal of the compressor needs to be periodically performed to maintain the air-conditioning unit. In such an instance, the air-conditioning unit is required to be renewed to one using HFC.
As such an air-conditioning unit, for example, there has been proposed an air-conditioning apparatus “using, as an alternative of the conventional R22 refrigerant, a HFC refrigerant, such as a R410A refrigerant that has a higher saturation pressure at a same temperature, as the refrigerant that is filled in the refrigeration cycle” (see Patent Literature 1, for example).